Photos show crocodile eating sawfish in Australia

The freshwater sawfish's signature snout makes it one of nature's most stealthy predators.

But in the murky waters of Western Australia's Fitzroy River, it offers little defence against sharks or crocodiles.

A new study, published in the journal Ecology, details the dangers posed there to the critically endangered species.

In it rare photos show a freshwater crocodile preying on a young sawfish.

The river system is a spawning area and a habitat for juvenile sawfish before they journey to the ocean to mature and breed.

Researchers and wildlife rangers examined 39 sawfish in the river and found evidence of bite marks on around 60%. Based on the appearance of the bite marks, the predators responsible were crocodiles and bull sharks, the study concludes.

Lead author, Associate Professor David Morgan, a fish biologist from Murdoch University said water levels are related to the survival of the young.

"The less water the more likely they are to encounter a predator such as a saltwater crocodile, particularly in the lower reaches of the river," he told the BBC.

Their unique snout, or rostrum, are prized as trophies and also make sawfish especially prone to entanglement in fishing nets.

Prof Morgan suggests that river crossings, weirs and dams be modified to allow the species to migrate upstream more safely.

"We now know that the Kimberly region of Western Australia is arguably the most important region for freshwater sawfish left on Earth," he said.

"They need the habitat and they need the water."